1. Field of the Invention
The present invention relates to a method of positioning a dental implant at an implant site. More particularly, the present invention relates to method of positioning a dental implant utilizing a dental cast, preparing a surgical guide, using the surgical guide as is, or in conjunction with the drilling of a model osteotomy, allowing pre-fabrication of an abutment and/or a temporary crown, and intra-oral placement of the dental implant.
2. Description of Related Art
Dental implants are an increasingly popular option for patients with missing teeth due to excessive decay, bone or gum damage, or accidents causing physical displacement and the like. Dental implants provide an attractive alternative to dentures because they look natural and require less maintenance. Implants further provide a stronger biting surface and allow patients to resume their normal diets.
In comparison to dentures and the like, however, dental implant procedures involve costly and complex surgical work. More accurately, dental implant procedures generally involve the placement of a dental implant or abutment in the underlying jawbone as a foundation, and the subsequent attachment of a prosthetic to the implant above the gum line. Generally, a dental osteotomy must be performed to prepare the bone for placement of the implant in order to place the implant. The implant is then inserted and fixed into the bone where it serves to hold the dental prosthetic. Accordingly, the osteotomy and implant placement must be precise.
The most difficult and skill intensive part of the implant procedure is generally positioning the drill to create the hole in the jawbone that will receive the implant. The hole must be formed at the precise location relative to adjacent teeth for a natural, attractive look. The hole must also be positioned in the proper location in the bone to ensure a solid base for the prosthetic. Inaccuracies in placing the hole can damage nearby vital structures such as nerves, blood vessels, sinus and neighboring teeth.
Improper placement of the hole for the implant also presents problems for the surgeon during the implant procedure. If the hole is not placed in the proper position in the jawbone, further drilling may be necessary. Even more troublesome, if bone has been mistakenly removed, new bone may have to be grafted or added to the site and let to heal for 3-6 months before a new attempt can be made.
For these reasons, implant procedures typically require the expertise of oral surgeons and usually are avoided by general dentists. Even some oral surgeons hesitate to do implant procedures because of the unique skills and experience required.
Positioning mistakes also require additional office visits by the patient, additional time to completion, and unnecessary discomfort. For this reason, it is highly desirable to reduce the risk of mistakenly drilling in an incorrect position.
Many tools and methods exist for increasing the accuracy, reliability, and ease with which a surgeon can perform the drilling operation. The most popular technique remains free-hand alignment. In the case of free-hand drilling, a surgeon draws upon his or her experience to determine the proper trajectory and final location of the implant. Not only does this require a steady hand, but the surgeon must also make a judgment as to where the bone is located below gum surface. Because the bone is masked under the gum tissue and because it is difficult to fully inspect the site, the surgeon typically has great difficulty in determining the proper position in this initial step.
The flap method is the typical method for overcoming the problem of determining bone position below the gum line. The flap method involves physically cutting a flap of skin near the site and surveying the implant site to determine the position of the jawbone. This method increases the risk of infection and provides further discomfort for the patient.
Free-hand drilling also presents safety hazards and accuracy problems. Although the surgeon can initially determine where to drill, during the drilling procedure, the drill bit can “jump” or slip. The drill bit can also “walk” or move before the tip of the bit grabs or digs into the bone. Additionally, free-hand drilling requires the surgeon to act without a complete view of the mouth interior and implant site.
Model-based or lab-based methods allow improved positioning by allowing less invasive surveying of the implant site. This method also provides for transferring of the measurements from the cast to the actual site. An exemplar of the prior art is U.S. Pat. No. 7,086,860 to Schuman et al. The Schuman method involves using tools to determine the size, angles, and positions for the dental implant on a model cast. The cast is cut to determine the bone position. A graphic is then drawn on the model and tools are used to transfer the placement information of the graphic to the implant site. In the laboratory, the buccal-lingual (“BL”) volume of bone is derived from the subtraction of the tissue depth as measured in the mouth through bone sounding. If the anatomy is followed, an accurate reflection of the available bone volume for implant placement may be determined. The mesio-distal (“MD”) positioning of the implant is derived from the transpositioning or translation of information from a radiograph onto the cast.
The above method has several limitations. The MD positioning in the lab is only an estimate and is not verifiable until transferred to a model and the mouth. Also, this method only allows the surgeon to practice drilling on a model and does not assist with transferring or accurately mapping the determined drilling position from the model back to the implant site. Cast models also do not overcome the drilling problems mentioned above.
U.S. Pat. No. 5,556,278 to Meitner is directed to a template to allow a surgeon to more accurately transfer the drilling location determined on the model to the implant site in the mouth. Meitner describes a tooth setup molded around the implant site and then placed on a cast model. The surgeon then drills through the setup. A guide post is inserted through the hole, and a sleeve is inserted over the guide post. A resin is then placed over the entire site with a separating medium between the resin and model. Once the resin dries, the resin is removed and can be used as a template to transfer the exact location from the model to the implant site. Further, the guide sleeve may act as a radiographic marker so the surgeon can determine the location and trajectory of the hole to be made in the bone by taking an X-ray with the template in place in the mouth.
Although the Meitner apparatus allows for relatively precise transfer of a drill location from a model to the implant site, errors still arise due to variations between the model and implant site. Further, the surgeon may decide on a position using the model and later reconsider when the template and sleeve are filmed at the implant site. In this case, the template must be formed again from the start and the patient will be required to make extra visits to the office and wait longer.
Another technique is based upon determining a trajectory for the drill using tools and aids and then translating the trajectory information to the implant site. An exemplar of such a technique is U.S. Pat. No. 5,015,183 to Fenick. Using X-rays, the surgeon determines where the implant should be positioned in the bone and then uses bushings to help guide the drill bit. Fenick also creates a radiology stent that includes a opaque grid. The stent, without any drill bushings, is X-rayed while in the patient's mouth. The stent is then placed over a model of the patient's jaw where the grid provides a frame of reference that helps in manually positioning a drill bit relative to the model jaw. A hole is drilled into the model, and the resulting hole helps align a drill bushing relative to the model. Next, a cast is created over the model to capture the drill bushing. The cast, with the drill bushing, is then placed in the patient's mouth to help guide the drill bit that drills a hole into the patient's jawbone. With the Fenick system, some positional accuracy may be sacrificed because the drill bushing is aligned to a model rather than being aligned directly to the patient's actual jaw.
In more recent years, computers and sophisticated peripheral imaging equipment have caused the positioning of implant systems to become far more sophisticated. Using radiographic and visual images of the mouth, one can construct detailed computer models such as computer aided drafting (CAD/CAM) drawings. The computer allows technicians and surgeons to experiment with many different positions and trajectories in three-dimensional computer space. A computer also allows a user to input various variables into the procedure and calculate the exact trajectory for the drill. Moreover, once the model is constructed and trajectory calculated, the data can be used to prototype a surgical guide for the drill.
Thus, computers in combination with many of the above procedures allow surgeons and technicians great flexibility in preparing for the osteotomy and implant procedure. These tools also allow the accurate translation of the data from the model to the implant site. However, such equipment can be extremely costly. Also, sophisticated equipment requires sophisticated technical skills and may be beyond the reach of those with limited technology skills.
Another method for performing implant osteotomies provides a method for readjusting the drill trajectory directly in the mouth. U.S. Pat. No. 7,097,451 to Tang describes a thermoplastic surgical template that allows adjustment after initially setting a drill position. The Tang template includes a base and a drill guide. The alignment of the drill guide may be determined using conventional methods. Alternatively, the template may be fastened in the mouth without setting an initial drill position.
The Tang template is constructed of a thermoplastic chosen with thermo-properties such that it can be heated to a state whereupon it can be molded. The thermoplastic then hardens when it cools. Thus, the surgeon can place the template, heat the template, readjust the drill guide with a specified tool, and then allow it to harden at the determined position. This process minimizes the number of office visits and steps in the osteotomy procedure. Surgeons can easily adjust the template at will without going through lots of steps or fabricating procedures.
Although the Tang template allows a surgeon to combine modeling with relatively accurate translation of the data to the implant site, such templates and methods lack readjustment control. The surgeon can readjust the template at the mouth site, but readjustment amounts to free-hand alignment. Once the thermoplastic is heated to a moldable state, the template flows freely in all directions. Essentially, the surgeon must reposition the drill guide in free space, meaning, in three dimensions with 360° of rotation. Additionally, the abutment and temporary crown can only be made after the surgical guide has been approved clinically because of the liberal readjustment procedure. Similar to the other methods described, the Tang method does not provide a controllable and quantifiable method of positioning relative to a dental cast.
In light of the forgoing, it would be beneficial to have a method and apparatus for aligning a dental implant which overcomes the above and other disadvantages of known implant positioning systems and methods. What is needed is an improved method and apparatus for controllably and quantifiably determining and adjusting a desired drilling trajectory that would allow accurately and repeatably performing a dental implant osteotomy and placing of a laboratory analog of an implant.